ENDOCRINE FUNCTION OF THE THYMUS GLAND 327 



The thymus glands of the test, as well as the control animals, 

 were carefully studied. We did not find, however, any regular 

 histological changes which might be attributed to the anti- 

 thymus serum injection. The dimension of each lobule, the pro- 

 portion of both cortical and medullary portions, and other 

 findings are similar in both the test and the control rats. 



In both test and control rats of series X, XI, and XII, we find 

 a rather high degree of atrophy of the thymus, as is shown 

 in the weight, and the sections also show some pecuharities: 

 atrophy of both medullary and cortical portions, and the pres- 

 ence of some round bodies similar in construction to the so-called 

 Hassel's bodies of some animals. 



These latter are located in the middle part of the medullary 

 portion. The diameter of such bodies varies from 28u to 34/^. 

 In construction such a body looks very much like the round 

 bodies in the epithelioma tissue described by Roffo ('18) in his 

 paper on the transmission of epithelioma in the white rat (also 

 Moorhead, '05) . Although this may be a pathological change in 

 the thymus tissue, yet it is not caused by the injected antithymus 

 serum, because the same structures are found in the thymus tissue 

 of the control rats also. We are inclined to attribute this his- 

 tological change in the thymus to malnutrition or to some 

 other condition from which the three litters of series X, XI, and 

 XII suffered, as already described during the experimental 

 period. 



Summing up the histological findings, we may conclude that 

 we do not find any alteration to be attributed to the antithymus 

 serum injection. 



4. IMMUNIZATION OF THE RABBIT WITH TESTES OF THE ALBINO 

 RAT (RABBIT, GROUP B) 



For the purpose of comparative study on the specificity of the 

 cytolitic serum against rat thymus, I attempted to get another 

 kind of cytolytic serum, and for this purpose immunized rabbits 

 against the testis tissue of albino rats. 



One large male rabbit received four injections of testis emul- 

 sion in physiological sahne solution as follows: 



